The present invention relates to an apparatus for connecting a rotor blade to a rotor hub, more specifically, for connecting a helicopter rotor blade to the hub of the drive shaft. Such connecting apparatus conventionally includes a blade connector bolt and a dampened connection between the rotor blade and the rotor hub.
The forces effective on a rotor or rather on a rotating blade and on the anchoring means connecting the blade to the rotor hub, comprise centrifugal force components as well as static and dynamic shearing force components and bending moments. Especially the bending moments are caused by periodically recurring wobbling and swivel motions of the rotor blade.
German Pat. No. 1,531,675 discloses in connection with hingeless rotors to take up the wobbling and swivel motions substantially ahead of the blade root to avoid the effect thereof on the connections of the blade to the rotor shaft. This is accomplished by constructing the neck section of the rotor blade to be yielding to bending moments but stiff relative to torsion. However, in such a construction it is not possible to increase the length of the neck section, which has a low resistance to bending, to any desired degree, because such an increase would adversely affect the aerodynamic characteristics of the rotor blade. Furthermore, it is unavoidable that the bending and shearing deformations in combination with the effective centrifugal forces are transmitted to the connecting hardware between the root of the rotor blade and the rotor drive shaft. As a result, these transmitted deformations and forces generate continuous friction forces between the blade grommet made of fiber reinforced synthetic material and the metal hardware. Such friction forces must be taken up or absorbed by the inner or inherent damping of the rotor blade and the connecting hardware. Since these forces cannot be precisely ascertained and since they may vary, the interfaces between the blade and the connecting hardware are subject to a continuous destructive wear and tear effect.